The circuit design for switching high currents—for example in the case of an converter—where space is at a premium, whilst keeping costs low and allowing mass production, is particularly critical. To this end, an arrangement of discrete power semiconductor devices (switching transistors) with current leads having a high current-carrying capacity and cooling of the power semiconductor devices, for example by means of a water cooling system, is required.
With regard to fast switching of the power semiconductor devices, this depends on a low-resistance and low-inductance connection of the components. However, this is only possible in the case of simple arrangements of DC link capacitors and power semiconductor devices. If additional components such as gate resistors are required, a low-inductance linkage of the power semiconductor devices to the DC link capacitors can no longer be guaranteed in all cases because the current-carrying copper surfaces are “cut” by the resistors and thus their resistance and inductance are increased.
As leakage inductances become greater, the overvoltage occurring at the power semiconductor devices increases. At the same time, the energy stored in the leakage inductances is converted into heat. The greater the currents to be switched, the greater this heat becomes because the energy increases with the square of the current. In the case of high currents, the leakage inductances must therefore be minimized since the power semiconductor devices could otherwise be destroyed. This also applies, however, appropriately scaled, to other circuits in which low currents are flowing.